Electronic Device With Fingerprint Sensor and Tunable Hybrid Antenna

ABSTRACT

An electronic device may have wireless circuitry and components such as sensors. The electronic device may have a metal housing having first and second planar rear wall portions separated by a gap. Conductive structures may bridge the gap to electrically couple the first and second rear wall portions. The wireless circuitry may include a hybrid slot inverted-F antenna. The antenna may have an inverted-F antenna resonating element formed from peripheral housing structures that are separated from the second rear wall portion by an opening. The opening may form a C-shaped slot antenna resonating element for the antenna. The sensors may include a fingerprint sensor. The fingerprint sensor may be coupled to a button member in a button. The fingerprint sensor and other portions of the button may overlap the second planar rear wall portion to minimize interference with antenna operation.

This application is a division of U.S. patent application Ser. No.14/463,299, filed Aug. 19, 2014, which is hereby incorporated byreference herein in its entirety. This application claims the benefit ofand claims priority to patent application Ser. No. 14/463,299, filedAug. 19, 2014.

BACKGROUND

This relates generally to electronic devices and, more particularly, toelectronic devices with components such as wireless components andsensors.

Electronic devices often include wireless circuitry with antennas. Forexample, cellular telephones, computers, and other devices often containantennas for supporting wireless communications. Sensors and otherelectrical components are also often included in electronic devices.

It can be challenging to form electronic device antenna structures withdesired attributes. In some wireless devices, the presence of conductivehousing structures, sensors, and other electrical components caninfluence antenna performance. Antenna performance may not besatisfactory if the housing structures or electrical components are notconfigured properly and interfere with antenna operation. Device sizecan also affect performance. It can be difficult to achieve desiredperformance levels in a compact device, particularly when the compactdevice has conductive housing structures.

It would therefore be desirable to be able to provide improved wirelesscircuitry and electrical components for electronic devices such aselectronic devices that include conductive housing structures.

SUMMARY

An electronic device may have wireless circuitry and components such assensors. The electronic device may have a metal housing having first andsecond planar rear wall portions separated by a gap. Conductivestructures may bridge the gap to electrically couple the first andsecond rear wall portions. The first rear wall portion may form anantenna ground. The second rear wall portion may form an extendedportion of the antenna ground.

The wireless circuitry may include a hybrid inverted-F slot antenna. Theantenna may have an inverted-F antenna resonating element formed fromperipheral housing structures that are separated from the second rearwall portion by an opening. The opening may form a C-shaped slot antennaresonating element for the antenna.

The sensors may include a fingerprint sensor. The fingerprint sensor maybe coupled to a button member in a button. The fingerprint sensor andother portions of the button may overlap the second planar rear wallportion to minimize interference with antenna operation.

An impedance matching circuit may be coupled to the antenna to match theimpedance of the antenna to a transmission line. An inductor that iscoupled in series with a switch may be coupled to the antenna. Antennaimpedance may be measured in real time using a coupler interposedbetween a transceiver and the antenna. Based on antenna impedancemeasurements, sensor data, or other information, control circuitry candetermine when an external object such as a user's hand is adjacent tothe antenna. The inductor may then be switched out of use with theswitch to ensure that the antenna is tuned satisfactorily.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an illustrative electronic device inaccordance with an embodiment.

FIG. 2 is a schematic diagram of illustrative circuitry in an electronicdevice in accordance with an embodiment.

FIG. 3 is a schematic diagram of illustrative wireless circuitry inaccordance with an embodiment.

FIG. 4 is a schematic diagram of an illustrative inverted-F antenna inaccordance with an embodiment.

FIG. 5 is a schematic diagram of an illustrative slot antenna inaccordance with an embodiment of the present invention.

FIG. 6 is a diagram of an illustrative hybrid inverted-F slot antenna inaccordance with an embodiment.

FIG. 7 is a diagram of an illustrative tunable antenna circuitry inaccordance with an embodiment.

FIG. 8 is a Smith chart illustrating how antenna tuning using a tunableimpedance matching network may be used to maintain a desired level ofantenna performance in the presence of contact between a user's hand andthe antenna in accordance with an embodiment.

FIG. 9 is a diagram showing how an electrical component such as afingerprint sensor may be located over a ground plane extension that isused in forming part of a hybrid antenna in accordance with anembodiment.

FIG. 10 is an interior top view of an illustrative end of an electronicdevice with conductive structures bridging a dielectric gap inaccordance with an embodiment.

FIG. 11 is an exterior view of an illustrative end of an electronicdevice with conductive structures of the type defined in claim 10.

FIG. 12 is a cross-sectional side view of an illustrative electronicdevice having an electrical component such as a fingerprint sensor thatoverlaps a ground plane extension associated with an antenna inaccordance with an embodiment.

DETAILED DESCRIPTION

Electronic devices such as electronic device 10 of FIG. 1 may beprovided with electrical components and wireless communicationscircuitry. The wireless communications circuitry may include one or moreantennas and may be used to support wireless communications in multiplewireless communications bands. An electrical component such as sensormay overlap an antenna in the wireless communications circuitry. Forexample, a fingerprint sensor may be mounted in a location where thefingerprint sensor overlaps an extended portion of an antenna groundplane. This location may help to minimize interference between thefingerprint sensor and antenna while allowing the fingerprint sensor tobe used to capture fingerprints.

The antennas of the wireless communications circuitry can include loopantennas, inverted-F antennas, strip antennas, planar inverted-Fantennas, slot antennas, hybrid antennas that include antenna structuresof more than one type, or other suitable antennas. Conductive structuresfor the antennas may, if desired, be formed from conductive electronicdevice structures. The conductive electronic device structures mayinclude conductive housing structures. The housing structures mayinclude peripheral structures such as peripheral conductive structuresthat run around the periphery of an electronic device. The peripheralconductive structure may serve as a bezel for a planar structure such asa display, may serve as sidewall structures for a device housing, mayhave portions that extend upwards from an integral planar rear housing(e.g., to form vertical planar sidewalls or curved sidewalls), and/ormay form other housing structures. Gaps may be formed in the peripheralconductive structures that divide the peripheral conductive structuresinto peripheral segments. One or more of the segments may be used informing one or more antennas for electronic device 10. Antennas may alsobe formed using an antenna ground plane formed from conductive housingstructures such as metal housing midplate structures and other internaldevice structures. Rear housing wall structures may be used in formingantenna structures such as an antenna ground.

Electronic device 10 may be a portable electronic device or othersuitable electronic device. For example, electronic device 10 may be alaptop computer, a tablet computer, a somewhat smaller device such as awrist-watch device, pendant device, headphone device, earpiece device,or other wearable or miniature device, a handheld device such as acellular telephone, a media player, or other small portable device.Device 10 may also be a television, a set-top box, a desktop computer, acomputer monitor into which a computer has been integrated, or othersuitable electronic equipment.

Device 10 may include a housing such as housing 12. Housing 12, whichmay sometimes be referred to as a case, may be formed of plastic, glass,ceramics, fiber composites, metal (e.g., stainless steel, aluminum,etc.), other suitable materials, or a combination of these materials. Insome situations, parts of housing 12 may be formed from dielectric orother low-conductivity material. In other situations, housing 12 or atleast some of the structures that make up housing 12 may be formed frommetal elements.

Device 10 may, if desired, have a display such as display 14. The rearface of housing 12 may have a planar housing wall. The rear housing wallmay be separated into first and second portions by a gap that is filledwith plastic or other dielectric. Conductive structures may electricallycouple the first and second portions together. Display 14 may be mountedon the opposing front face of device 10 from the rear housing wall.Display 14 may be a touch screen that incorporates capacitive touchelectrodes or may be insensitive to touch.

Display 14 may include image pixels formed from light-emitting diodes(LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels,electrophoretic pixels, liquid crystal display (LCD) components, orother suitable image pixel structures. A display cover layer such as alayer of clear glass or plastic may cover the surface of display 14.Buttons such as button 24 may pass through openings in the cover layer.The cover layer may also have other openings such as an opening forspeaker port 26.

Housing 12 may include peripheral housing structures such as structures16. Structures 16 may run around the periphery of device 10 and display14. In configurations in which device 10 and display 14 have arectangular shape with four edges, structures 16 may be implementedusing peripheral housing structures that have a rectangular ring shapewith four corresponding edges (as an example). Peripheral structures 16or part of peripheral structures 16 may serve as a bezel for display 14(e.g., a cosmetic trim that surrounds all four sides of display 14and/or that helps hold display 14 to device 10). Peripheral structures16 may also, if desired, form sidewall structures for device 10 (e.g.,by forming a metal band with vertical sidewalls, curved sidewalls,etc.).

Peripheral housing structures 16 may be formed of a conductive materialsuch as metal and may therefore sometimes be referred to as peripheralconductive housing structures, conductive housing structures, peripheralmetal structures, or a peripheral conductive housing member (asexamples). Peripheral housing structures 16 may be formed from a metalsuch as stainless steel, aluminum, or other suitable materials. One,two, or more than two separate structures may be used in formingperipheral housing structures 16.

It is not necessary for peripheral housing structures 16 to have auniform cross-section. For example, the top portion of peripheralhousing structures 16 may, if desired, have an inwardly protruding lipthat helps hold display 14 in place. The bottom portion of peripheralhousing structures 16 may also have an enlarged lip (e.g., in the planeof the rear surface of device 10). Peripheral housing structures 16 mayhave substantially straight vertical sidewalls, may have sidewalls thatare curved, or may have other suitable shapes. In some configurations(e.g., when peripheral housing structures 16 serve as a bezel fordisplay 14), peripheral housing structures 16 may run around the lip ofhousing 12 (i.e., peripheral housing structures 16 may cover only theedge of housing 12 that surrounds display 14 and not the rest of thesidewalls of housing 12).

If desired, housing 12 may have a conductive rear surface. For example,housing 12 may be formed from a metal such as stainless steel oraluminum. The rear surface of housing 12 may lie in a plane that isparallel to display 14. In configurations for device 10 in which therear surface of housing 12 is formed from metal, it may be desirable toform parts of peripheral conductive housing structures 16 as integralportions of the housing structures forming the rear surface of housing12. For example, a rear housing wall of device 10 may be formed from aplanar metal structure and portions of peripheral housing structures 16on the sides of housing 12 may be formed as vertically extendingintegral metal portions of the planar metal structure. Housingstructures such as these may, if desired, be machined from a block ofmetal and/or may include multiple metal pieces that are assembledtogether to form housing 12. The planar rear wall of housing 12 may haveone or more, two or more, or three or more portions.

Display 14 may include conductive structures such as an array ofcapacitive electrodes, conductive lines for addressing pixel elements,driver circuits, etc. Housing 12 may include internal structures such asmetal frame members, a planar housing member (sometimes referred to as amidplate) that spans the walls of housing 12 (i.e., a substantiallyrectangular sheet formed from one or more parts that is welded orotherwise connected between opposing sides of member 16), printedcircuit boards, and other internal conductive structures. Theseconductive structures, which may be used in forming a ground plane indevice 10, may be located in the center of housing 12 under active areaAA of display 14 (e.g., the portion of display 14 that contains adisplay module for displaying images).

In regions 22 and 20, openings may be formed within the conductivestructures of device 10 (e.g., between peripheral conductive housingstructures 16 and opposing conductive ground structures such asconductive housing midplate or rear housing wall structures, a printedcircuit board, and conductive electrical components in display 14 anddevice 10). These openings, which may sometimes be referred to as gaps,may be filled with air, plastic, and other dielectrics.

Conductive housing structures and other conductive structures in device10 such as a midplate, traces on a printed circuit board, display 14,and conductive electronic components may serve as a ground plane for theantennas in device 10. The openings in regions 20 and 22 may serve asslots in open or closed slot antennas, may serve as a central dielectricregion that is surrounded by a conductive path of materials in a loopantenna, may serve as a space that separates an antenna resonatingelement such as a strip antenna resonating element or an inverted-Fantenna resonating element from the ground plane, may contribute to theperformance of a parasitic antenna resonating element, or may otherwiseserve as part of antenna structures formed in regions 20 and 22. Ifdesired, the ground plane that is under active area AA of display 14and/or other metal structures in device 10 may have portions that extendinto parts of the ends of device 10 (e.g., the ground may extend towardsthe dielectric-filled openings in regions 20 and 22).

In general, device 10 may include any suitable number of antennas (e.g.,one or more, two or more, three or more, four or more, etc.). Theantennas in device 10 may be located at opposing first and second endsof an elongated device housing (e.g., at ends 20 and 22 of device 10 ofFIG. 1), along one or more edges of a device housing, in the center of adevice housing, in other suitable locations, or in one or more of theselocations. The arrangement of FIG. 1 is merely illustrative.

Portions of peripheral housing structures 16 may be provided with gapstructures. For example, peripheral housing structures 16 may beprovided with one or more gaps such as gaps 18, as shown in FIG. 1. Thegaps in peripheral housing structures 16 may be filled with dielectricsuch as polymer, ceramic, glass, air, other dielectric materials, orcombinations of these materials. Gaps 18 may divide peripheral housingstructures 16 into one or more peripheral conductive segments. There maybe, for example, two peripheral conductive segments in peripheralhousing structures 16 (e.g., in an arrangement with two gaps), threeperipheral conductive segments (e.g., in an arrangement with threegaps), four peripheral conductive segments (e.g., in an arrangement withfour gaps, etc.). The segments of peripheral conductive housingstructures 16 that are formed in this way may form parts of antennas indevice 10. If desired, gaps may extend across the width of the rear wallof housing 12 and may penetrate through the rear wall of housing 12 todivide the rear wall into different portions. Polymer or otherdielectric may fill these housing gaps (grooves).

In a typical scenario, device 10 may have upper and lower antennas (asan example). An upper antenna may, for example, be formed at the upperend of device 10 in region 22. A lower antenna may, for example, beformed at the lower end of device 10 in region 20. The antennas may beused separately to cover identical communications bands, overlappingcommunications bands, or separate communications bands. The antennas maybe used to implement an antenna diversity scheme or amultiple-input-multiple-output (MIMO) antenna scheme.

Antennas in device 10 may be used to support any communications bands ofinterest. For example, device 10 may include antenna structures forsupporting local area network communications, voice and data cellulartelephone communications, global positioning system (GPS) communicationsor other satellite navigation system communications, Bluetooth®communications, etc.

A schematic diagram showing illustrative components that may be used indevice 10 of FIG. 1 is shown in FIG. 2. As shown in FIG. 2, device 10may include control circuitry such as storage and processing circuitry28. Storage and processing circuitry 28 may include storage such as harddisk drive storage, nonvolatile memory (e.g., flash memory or otherelectrically-programmable-read-only memory configured to form a solidstate drive), volatile memory (e.g., static or dynamicrandom-access-memory), etc. Processing circuitry in storage andprocessing circuitry 28 may be used to control the operation of device10. This processing circuitry may be based on one or moremicroprocessors, microcontrollers, digital signal processors,application specific integrated circuits, etc.

Storage and processing circuitry 28 may be used to run software ondevice 10, such as internet browsing applications,voice-over-internet-protocol (VOIP) telephone call applications, emailapplications, media playback applications, operating system functions,etc. To support interactions with external equipment, storage andprocessing circuitry 28 may be used in implementing communicationsprotocols. Communications protocols that may be implemented usingstorage and processing circuitry 28 include internet protocols, wirelesslocal area network protocols (e.g., IEEE 802.11 protocols—sometimesreferred to as WiFi®), protocols for other short-range wirelesscommunications links such as the Bluetooth® protocol, cellular telephoneprotocols, MIMO protocols, antenna diversity protocols, etc.

Input-output circuitry 30 may include input-output devices 32.Input-output devices 32 may be used to allow data to be supplied todevice 10 and to allow data to be provided from device 10 to externaldevices. Input-output devices 32 may include user interface devices,data port devices, and other input-output components. For example,input-output devices may include touch screens, displays without touchsensor capabilities, buttons, joysticks, scrolling wheels, touch pads,key pads, keyboards, microphones, cameras, buttons, speakers, statusindicators, light sources, audio jacks and other audio port components,digital data port devices, light sensors, motion sensors(accelerometers), capacitance sensors, proximity sensors, fingerprintsensors (e.g., a fingerprint sensor integrated with a button such asbutton 24 of FIG. 1), etc.

Input-output circuitry 30 may include wireless communications circuitry34 for communicating wirelessly with external equipment. Wirelesscommunications circuitry 34 may include radio-frequency (RF) transceivercircuitry formed from one or more integrated circuits, power amplifiercircuitry, low-noise input amplifiers, passive RF components, one ormore antennas, transmission lines, and other circuitry for handling RFwireless signals. Wireless signals can also be sent using light (e.g.,using infrared communications).

Wireless communications circuitry 34 may include radio-frequencytransceiver circuitry 90 for handling various radio-frequencycommunications bands. For example, circuitry 34 may include transceivercircuitry 36, 38, and 42. Transceiver circuitry 36 may handle 2.4 GHzand 5 GHz bands for WiFi® (IEEE 802.11) communications and may handlethe 2.4 GHz Bluetooth® communications band. Circuitry 34 may usecellular telephone transceiver circuitry 38 for handling wirelesscommunications in frequency ranges such as a low communications bandfrom 700 to 960 MHz, a midband from 1710 to 2170 MHz, and a high bandfrom 2300 to 2700 MHz or other communications bands between 700 MHz and2700 MHz or other suitable frequencies (as examples). Circuitry 38 mayhandle voice data and non-voice data. Wireless communications circuitry34 can include circuitry for other short-range and long-range wirelesslinks if desired. For example, wireless communications circuitry 34 mayinclude 60 GHz transceiver circuitry, circuitry for receiving televisionand radio signals, paging system transceivers, near field communications(NFC) circuitry, etc. Wireless communications circuitry 34 may includeglobal positioning system (GPS) receiver equipment such as GPS receivercircuitry 42 for receiving GPS signals at 1575 MHz or for handling othersatellite positioning data. In WiFi® and Bluetooth® links and othershort-range wireless links, wireless signals are typically used toconvey data over tens or hundreds of feet. In cellular telephone linksand other long-range links, wireless signals are typically used toconvey data over thousands of feet or miles.

Wireless communications circuitry 34 may include antennas 40. Antennas40 may be formed using any suitable antenna types. For example, antennas40 may include antennas with resonating elements that are formed fromloop antenna structures, patch antenna structures, inverted-F antennastructures, slot antenna structures, planar inverted-F antennastructures, helical antenna structures, hybrids of these designs, etc.Different types of antennas may be used for different bands andcombinations of bands. For example, one type of antenna may be used informing a local wireless link antenna and another type of antenna may beused in forming a remote wireless link antenna.

As shown in FIG. 3, transceiver circuitry 90 in wireless circuitry 34may be coupled to antenna structures 40 using paths such as path 92.Wireless circuitry 34 may be coupled to control circuitry 28. Controlcircuitry 28 may be coupled to input-output devices 32. Input-outputdevices 32 may supply output from device 10 and may receive input fromsources that are external to device 10.

To provide antenna structures such as antenna(s) 40 with the ability tocover communications frequencies of interest, antenna(s) 40 may beprovided with circuitry such as filter circuitry (e.g., one or morepassive filters and/or one or more tunable filter circuits). Discretecomponents such as capacitors, inductors, and resistors may beincorporated into the filter circuitry. Capacitive structures, inductivestructures, and resistive structures may also be formed from patternedmetal structures (e.g., part of an antenna). If desired, antenna(s) 40may be provided with adjustable circuits such as tunable components 102to tune antennas over communications bands of interest. Tunablecomponents 102 may be part of a tunable filter or tunable impedancematching network, may be part of an antenna resonating element, may spana gap between an antenna resonating element and antenna ground, etc.Tunable components 102 may include tunable inductors, tunablecapacitors, or other tunable components. Tunable components such asthese may be based on switches and networks of fixed components,distributed metal structures that produce associated distributedcapacitances and inductances, variable solid state devices for producingvariable capacitance and inductance values, tunable filters, or othersuitable tunable structures. During operation of device 10, controlcircuitry 28 may issue control signals on one or more paths such as path93 that adjust inductance values, capacitance values, or otherparameters associated with tunable components 102, thereby tuningantenna structures 40 to cover desired communications bands.

Path 92 may include one or more transmission lines. As an example,signal path 92 of FIG. 3 may be a transmission line having a positivesignal conductor such as line 94 and a ground signal conductor such asline 96. Lines 94 and 96 may form parts of a coaxial cable or amicrostrip transmission line (as examples). A matching network formedfrom components such as inductors, resistors, and capacitors may be usedin matching the impedance of antenna(s) 40 to the impedance oftransmission line 92. Matching network components may be provided asdiscrete components (e.g., surface mount technology components) or maybe formed from housing structures, printed circuit board structures,traces on plastic supports, etc. Components such as these may also beused in forming filter circuitry in antenna(s) 40 and may be tunableand/or fixed components.

Transmission line 92 may be coupled to antenna feed structuresassociated with antenna structures 40. As an example, antenna structures40 may form an inverted-F antenna, a slot antenna, a hybrid inverted-Fslot antenna or other antenna having an antenna feed with a positiveantenna feed terminal such as terminal 98 and a ground antenna feedterminal such as ground antenna feed terminal 100. Positive transmissionline conductor 94 may be coupled to positive antenna feed terminal 98and ground transmission line conductor 96 may be coupled to groundantenna feed terminal 92. Other types of antenna feed arrangements maybe used if desired. The illustrative feeding configuration of FIG. 3 ismerely illustrative.

A directional coupler such as coupler 95 may be interposed intransmission line path 92. Control circuitry 28 and transceivercircuitry 90 may gather phase and magnitude information on the impedanceof antenna 40 (or part of antenna 40) using directional coupler 95. Byusing coupler 95 or other circuitry to gather real time information onthe impedance of antenna 40, control circuitry 28 can determine whenantenna 40 is being loaded by external objects (e.g., when a user's handis in the vicinity of antenna 40 and is therefore affecting theimpedance of antenna 40). In response to detecting that a user's hand orother external object is adjacent to antenna 40, control circuitry 28may take corrective action. For example, control circuitry 28 may adjustan adjustable inductor or other tunable component 102 to ensure thatantenna 40 operates as desired. If desired, control circuitry 28 may useinformation from a proximity sensor (see, e.g., sensors 32 of FIG. 2),received signal strength information, or other information indetermining when antenna 40 is being affected by the presence of nearbyexternal objects. The use of antenna feedback from directional coupler95 is merely illustrative.

FIG. 4 is a diagram of illustrative inverted-F antenna structures thatmay be used in implementing antenna 40 for device 10. Inverted-F antenna40 of FIG. 4 has antenna resonating element 106 and antenna ground(ground plane) 104. Antenna resonating element 106 may have a mainresonating element arm such as arm 108. The length of arm 108 and/orportions of arm 108 may be selected so that antenna 40 resonates atdesired operating frequencies. For example, if the length of arm 108 maybe a quarter of a wavelength at a desired operating frequency forantenna 40. Antenna 40 may also exhibit resonances at harmonicfrequencies.

Main resonating element arm 108 may be coupled to ground 104 by returnpath 110. Antenna feed 112 may include positive antenna feed terminal 98and ground antenna feed terminal 100 and may run in parallel to returnpath 110 between arm 108 and ground 104. If desired, inverted-F antennassuch as illustrative antenna 40 of FIG. 4 may have more than oneresonating arm branch (e.g., to create multiple frequency resonances tosupport operations in multiple communications bands) or may have otherantenna structures (e.g., parasitic antenna resonating elements, tunablecomponents to support antenna tuning, etc.). For example, arm 108 mayhave left and right branches that extend outwardly from feed 112 andreturn path 110.

Antenna 40 may include a slot antenna resonating element. As shown inFIG. 5, for example, antenna 40 may be a slot antenna having an openingsuch as slot 114 that is formed within antenna ground 104. Slot 114 maybe filled with air, plastic, and/or other dielectric. The shape of slot114 may be straight or may have one or more bends (i.e., slot 114 mayhave an elongated shape following a meandering path). The antenna feedfor antenna 40 may include positive antenna feed terminal 98 and groundantenna feed terminal 100. Feed terminals 98 and 100 may, for example,be located on opposing sides of slot 114 (e.g., on opposing long sides).Slot-based antenna resonating elements such as slot antenna resonatingelement 114 of FIG. 5 may give rise to an antenna resonance atfrequencies in which the wavelength of the antenna signals is equal tothe perimeter of the slot. In narrow slots, the resonant frequency of aslot antenna resonating element is associated with signal frequencies atwhich the slot length is equal to a half of a wavelength. Slot antennafrequency response can be tuned using one or more tunable componentssuch as tunable inductors or tunable capacitors. These components mayhave terminals that are coupled to opposing sides of the slot (i.e., thetunable components may bridge the slot). If desired, tunable componentsmay have terminals that are coupled to respective locations along thelength of one of the sides of slot 114. Combinations of thesearrangements may also be used.

If desired, antenna 40 may incorporate conductive device structures suchas portions of housing 12. As an example, peripheral conductivestructures 16 may include multiple portions such as segments 16B and 16Eof FIG. 6. Peripheral conductive structures 16E may be conductivestructures that run along the left and right edges of antenna groundplane 104 (e.g., housing sidewalls that are separate from the rear ofhousing 12 or that are integral portions of housing 12 that extendupwards from the rear wall of housing 12). Ground plane 104 may beformed by portions of a metal housing midplate member, a metal rearhousing wall, conductive portions of display 14, or other conductiveantenna ground structures. Peripheral conductive structures 16B may runalong the end of device 10 (e.g., the lower peripheral edge of device 10in the example of FIG. 6) and may have shorter portions that run alongsections of the left and right edges of device 10.

Along the periphery of device 10, structures 16B and 16E may beseparated by gaps such as gaps 18. Gaps 18 may be filled with adielectric such as polymer. Ground plane 104 may have an extendedportion such as extended portion 104E that extends into the spacebetween structures 16B and the rest of ground plane 104 (i.e., theportion of the ground formed from display 14, a metal housing midplate,and/or the central portion of the planar rear wall of housing 12).

In the example of FIG. 6, antenna 40 has been formed at lower end 20 ofdevice 10. This is merely illustrative. Antennas such as antenna 40 ofFIG. 6 may be formed at opposing ends of device 10 or different antennasmay be formed at each end of device 10. Configurations with more thantwo antennas for device 10 may also be used.

Antenna 40 may be a hybrid antenna such as a hybrid inverted-F slotantenna having both slot and inverted-F antenna portions. Ground 104(including ground plane extension 104E) may form an antenna ground forantenna 40. The slot portion of antenna 40 of FIG. 6 may be formed fromslot 114 between peripheral conductive structures 16B and ground planeextension 104E of ground 104. Slot 114 may have a C shape as shown inFIG. 6 (i.e., slot 114 may be a C-shaped slot that runs along peripheraledges of device 10 and housing 12) or may have other slots shapes withbends. Straight slots without bends may also be used in forming antenna40, if desired. The inverted-F portion of antenna 40 of FIG. 6 may beformed from an inverted-F resonating element such as peripheralconductive structures 16B and ground 104 (ground plane extension 104E).

A conductive path such as a strip of metal or metal trace on a printedcircuit or plastic carrier may form return path 110 for the inverted-Fportion of antenna 40. Return path 110 may be coupled between structures16B and ground 104 in parallel with feed 112. Antenna tuning may beprovided by a tunable circuitry (e.g., a tunable impedance matchingcircuit or other circuit coupled to antenna 40 at feed terminals 98 and100 in antenna feed 112) and/or by tunable components such as adjustableinductor 120. Adjustable inductor 120 may span the dielectric gap formedby slot opening 114 and may be coupled between structures 16B and groundextension 104E in parallel with feed 112. Adjustable inductor 120 may beadjusted to tune the frequency associated with the low communicationsband of antenna 40 or may be used to make other antenna tuningadjustments for antenna 40. There may be capacitances associated withgaps 18. If desired, fixed or tunable inductors may be coupled acrossgaps 18 to counteract the capacitance associated with gaps 18.

As described in connection with resonating element arm 108 of inverted-Fantenna resonating element 106 of FIG. 4, peripheral conductive housingstructures 16B may form an inverted-F antenna resonating element thatcovers one or more communications bands of interest. As an example,peripheral conductive housing structures 16B may have a first portionsuch as portion LB of FIG. 6 that supports a resonance at a lowcommunications band (e.g., a band covering frequencies from 700 MHz to960 MHz or other frequency range) and may have a second portion such asportion MB of FIG. 6 that supports a resonance at a mid-frequency (“midband”) communications band (e.g., a band covering frequencies from 1710MHz to 2170 MHz or other frequency range). Slot 114 may serve as a slotresonating element that supports a resonance at a high communicationsband (e.g., a band covering frequencies from 2300 MHz to 2700 MHz orother frequency range). The low band, middle band, and high band may liewithin a frequency range between 700 MHz and 2700 MHz or other suitablefrequency range. If desired, other inverted-F slot hybrid antennaconfigurations may be used. The example of FIG. 6 in which theinverted-F portion of the hybrid antenna supports low and mid bandcommunications bands and in which the slot antenna resonating elementsupports communications in a high band is merely illustrative.

Transmission line 92 may have an impedance of 50 ohms or other suitableimpedance. To help match the impedance of antenna 40 to the impedance oftransmission line 92 and thereby enhance antenna performance, device 10may be provided with an impedance matching circuit. For example, animpedance matching circuit such as matching circuitry 138 of FIG. 7 maybe coupled between positive antenna feed terminal 98 and ground antennafeed terminal 100. Ground terminals 136 may be coupled to ground 104(e.g., extension 104E). Matching circuit 126 may include one or morecomponents that form an impedance matching network such as inductors,capacitors, and resistors. Matching circuit 126 may be coupled betweenterminals 98 and 100. Tunable inductor 120 (FIG. 6), which may becoupled across slot 114 as shown in FIG. 6, may be implemented usingswitching circuitry 128 and inductors such as inductors 130, 132, and134. Inductors 130, 132, and 134 may have different values or two ormore of these inductors may have the same value. Switching circuitry 128may switch one or more of the inductors into use to adjust the overallinductance of adjustable inductor 120. For example, control circuitry 28can adjust switching circuitry 128 to adjust the inductance of inductor120 so that antenna 40 can cover a desired communications band (e.g.,inductor 120 may be adjusted to tune the low band).

Switching circuit (switch) 124 and inductor 122 may be connected inseries and may be coupled to antenna 40 (e.g., at a feed terminal orother location). As an example, switch 124 and inductor 122 may becoupled across one of gaps 18 (or multiple such switchable inductors maybe provided). Switch 124 may be controlled by control circuitry 28 andmay be used to switch inductor 122 into use and out of use to compensatefor potential antenna detuning in the presence of an external object inthe vicinity of antenna 40 (e.g., in the vicinity of gap(s) 18). Duringoperation in the absence of a hand or other external object adjacent toantenna 40, switch 124 may be closed and inductor 122 may be switchedinto use. When a hand of a user or other external object is present inthe vicinity of gap(s) 18 (i.e., adjacent to antenna 40), thecapacitance of gap(s) 18 may rise. This rise in capacitance has thepotential to detune antenna 40. The presence of the user's hand may bedetected using a proximity sensor (e.g., a capacitive proximity sensor,a light-based proximity sensor, etc.), using a temperature sensor, usinga camera, using an impedance measuring circuit (e.g., feedback fromdirectional coupler 95) to measure the impedance of antenna 40 or aportion of antenna 40 in real time, or using other detection techniques.

Due to the potential of a user's grip to detune antenna, switch 124 maybe placed in an open condition whenever the presence of an externalobject in the vicinity of antenna 40 is detected. When switch 124 isopened in response to detection of the presence of the user's hand orother external object adjacent to antenna 40, inductor 122 will beswitched out of use and the frequency response (tuning) of antenna 40will be maintained as desired.

FIG. 8 is a Smith chart illustrating the impact of using switchingcircuitry such as switch 124 to switch inductor 122 into and out of use.Transmission line 92 may have an impedance of 50 ohms (as an example),as illustrated by impedance 140. When antenna 40 is operating normally(across a range of frequencies between 700 MHz and 2700 MHz or otherfrequency range), antenna 40 may exhibit an impedance such asillustrative impedance 142. Impedance 142 may be associated with the useof inductor 122 of FIG. 7 (i.e., antenna 40 will have impedance 142 wheninductor 122 is switched into use by closing switch 124).

Impedance 142 is closely matched to transmission line impedance 140 asdesired. Upon placing a user's hand or other external object in thepresence of gap(s) 18 (i.e., adjacent to antenna 40), antenna impedance142 may be detuned to impedance 146, unless switch 124 is opened andinductor 122 is switched out of use. When switch 124 is opened andinductor 122 is switched out of use to adjust the operation of antenna40 in response to detecting that the user's hand or other externalobject is present in the vicinity of gap(s) 18 (i.e., detecting that theuser's hand is adjacent to antenna 40), antenna 40 will exhibitsatisfactory impedance 144. The use of switch 124 to switch inductor 122in and out of use based on the absence or presence of the user's hand,respectively, may therefore ensure that antenna 40 is not detuned by anunacceptable amount.

FIG. 9 shows how an electronic component may be mounted in the vicinityof antenna 40 without disrupting the performance of antenna 40. In theexample of FIG. 9, button 24 has been provided with a fingerprint sensorsuch as fingerprint sensor 152. Fingerprint sensor 152 may include ametal outer ring such as ring 150 or other electrode that supplies analternating current signal. Ring 150 may surround central area 156.Fingerprint sensor electrodes 154 may be formed in a one-dimensional ortwo-dimensional array in area 156. When a user places a finger overregion 156, signals may be injected into the user's finger from ring 150and picked up by the array of electrodes 154 in region 156. This allowsthe fingerprint sensor 152 to measure fingerprint patterns for theuser's finger. A captured fingerprint or other data from fingerprintsensor 152 may be conveyed to control circuitry 28 using metal signaltraces on flexible printed circuit 158.

Flexible printed circuit 158 may have an end portion such as portion 160that overlaps extended portion 104E of ground 104. Because the metaltraces on portion 160 and the metal structures of fingerprint sensor 152overlap ground plane extension 104E, antenna 40 operates properlywithout interference from the presence of fingerprint sensor 152. In theexample of FIG. 9, fingerprint sensor 152 overlaps extended portion 104Eand is mounted on a flexible printed circuit that extends betweenextended portion 104E and ground 104 in the center of device 10. This ismerely illustrative. Fingerprint sensor 152 may be located in otherportions of device 10 on ground plane extension 104E or elsewhereoverlapping ground 104.

FIG. 10 shows how ground plane extension 104E may be shorted to groundplane 104 through shorting structures 164. Shorting structures 164 mayinclude conductive structures 166 such as strips of metal foil, metalhousing structures, metal traces on one or more flexible printedcircuits, laser direct structuring metal traces on a plastic carrier,other metal on a dielectric carrier, metal clips, lengths of wire, orother conductive structures that electrically couple ground plane 104 toground plane extension 104E. Ground plane 104 and ground plane extension104E in this type of arrangement may be formed from machined metal parts(e.g., planar metal structures such as respective portions of a planarrear wall for housing 12). Conductive structures 166 may be coupledbetween ground plane 104 and ground plane extension 104E using solder,welds, conductive adhesive, screws or other fasteners, or otherconductive coupling structures.

Metal housing 12 may have gaps such as gaps 114 and 162 of FIG. 10.These gaps may be filled with plastic or other dielectric. Gap 114 mayseparate ground plane extension 104E from peripheral metal housingstructures 16B. Gap 162 may separate the planar rear wall portion ofmetal housing 12 that forms structure 104E from the planar rear wallportion of metal housing 12 that forms ground 104. Gap 162 may bebridged using shorting structures 164. The shorting structureselectrically couple the portions of housing forming ground 104 andground extension 104E, so that ground extension 104E serves as anextension of ground 104.

Shorting structures 164 of FIG. 10 may be formed on the interior ofdevice 10. When viewed from the exterior of device 10, gap 114 and gap162 may appear as shown in FIG. 11. As shown in FIG. 11, gaps 114 and162 may be filled with a dielectric material such as plastic. Theplastic may lie flush with the outer surface of housing 12. The plasticin gap 162 may cover internal structures such as shorting structures 164and may therefore hide these internal structures from view.

FIG. 12 is a cross-sectional side view of device 10 showing howfingerprint sensor 152 may be formed within button 24 in a portion ofdevice 10 that overlaps ground extension 104E. As shown in FIG. 12,display 14 may have a display cover layer such as display cover layer178 and a display module such as display module 180. Display cover layer178 may be formed from a clear layer of glass, a transparent plasticlayer, or other transparent material. Display module 180 may be a liquidcrystal display module, may be an organic light-emitting diode displaymodule, or may include display layers formed using other types ofdisplay technology. Display module 180 may be located in the center ofdevice 10 overlapping the portion of housing 12 associated with groundplane 104. Active area AA of FIG. 1 may cover display module 180 of FIG.12.

Ground plane 104 of FIG. 12 may be formed from conductive structuressuch as housing 12, display module 180, a metal midplate (not shown inFIG. 12), metal traces on printed circuit boards, etc. For example,ground plane 104 may be formed from a first planar portion of the rearwall of housing 12. Display module 180 may overlap the central portionof antenna ground (i.e., the portion of ground 104 that is separatedfrom extended ground portion 104E by gap 162) without overlappingextended ground portion 104E. Display cover layer 178 may overlap boththe portion of ground 104 that is overlapped by display module 180 andextended ground portion 104E. Extended ground portion 104E may be formedfrom a second planar portion of the rear wall of housing 12.

Plastic may be used to fill gap 162 between the portion of housing 12forming ground plane 104 and the portion of housing 12 forming groundplane extension 104E. Conductive structures 166 may electrically connectground plane extension 104E to housing 12 in ground plane 104. Supportstructures such as structure 184 and receptacle 174 may form a femaleconnector that receives male connector 182 (e.g., a connector coupled tothe end of a cable or other accessory). Button 24 may overlap theconnector that receives plug 182 (i.e., button 24 may overlap plugreceptacle 174). Peripheral conductive structures 16B may form a housingwall at the end of housing 12 (e.g., the lower end of housing 12). Anopening may be formed in peripheral conductive structures 16B toaccommodate connector 182.

Button 24 may be formed from a button member such as button member 170surrounded by metal trim 150 (e.g., a metal ring). Button member 170 maybe formed from a dielectric such as plastic or glass (as examples).Button 24 may include fingerprint sensor 152. Fingerprint sensor 152 maybe mounted under button member 170 (as an example). During operation,fingerprint sensor electrodes 154 in sensor 152 may be capacitivelycoupled to a user's finger through the dielectric of button member 170.Metal ring 150 in button 24 may provide alternating current signals thatare coupled to electrodes 154 through a user's finger during fingerprintcapture operations. Sensor 152 may be coupled to metal traces onflexible printed circuit 158.

Button 24 may have a switch such as switch 172. Switch 172 may bemounted on the lower surface of fingerprint sensor 152, so that button24 and fingerprint sensor 152 in button 24 overlap switch 172 (as anexample). When button 24 (i.e., button member 170) is pressed in adownwards direction (towards the interior of device 10), switch 172 willbe compressed between button member 170 and underlying structures suchas receptacle 174 or other support structures. When compressed, button24 will change state (i.e., button 24 will transition from open toclosed or vice versa due to actuation of switch 170). Switch 170 may bea dome switch or other suitable switch. Configurations for button 24that use a capacitive touch sensor to implement button functionality(e.g., a switchless button) may be used, if desired. Because button 24and fingerprint sensor 152 in button 24 overlap ground plane extension104E, the operation of antenna 40 will not be disrupted by the presenceof button 24 and fingerprint sensor 152.

The foregoing is merely illustrative and various modifications can bemade by those skilled in the art without departing from the scope andspirit of the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device comprising: a metal housinghaving a rear wall with a first rear wall portion and a second rear wallportion separated by a dielectric-filled gap; conductive structures thatbridge the gap and electrically couple the first rear wall portion tothe second rear wall portion; and a fingerprint sensor that overlapsthat second rear wall portion.
 2. The electronic device defined in claim1 further comprising: an antenna, wherein the rear wall forms an antennaground for the antenna and the antenna ground has an extended groundportion formed from the second rear wall portion
 3. The electronicdevice defined in claim 2 wherein the antenna comprises a slot antennaresonating element formed from an opening between the extended groundportion and peripheral conductive structures in the metal housing. 4.The electronic device defined in claim 3 wherein the opening is aC-shaped slot.
 5. The electronic device defined in claim 3 furthercomprising: a feed terminal coupled to the peripheral conductivestructures, wherein the peripheral conductive structures form aninverted-F antenna resonating element in the antenna and an adjustableinductor for tuning a communications band for the antenna is coupledbetween the peripheral conductive structures and extended groundportion; and a switch and inductor that are coupled in series and thatare coupled to the antenna, wherein the switch is configured to switchthe inductor out of use in response to determining that an externalobject is present adjacent to the antenna.
 6. The electronic devicedefined in claim 1, further comprising: a flexible printed circuit,wherein the fingerprint sensor is mounted to the flexible printedcircuit and a portion of the flexible printed circuit on which thefingerprint sensor is mounted overlaps the second rear wall portion. 7.The electronic device defined in claim 1, further comprising: a buttonthat has a switch, wherein the fingerprint sensor is mounted within thebutton.
 8. The electronic device defined in claim 1, wherein the metalhousing comprises first and second peripheral sidewalls and the firstrear wall portion extends between the first and second peripheralsidewalls and is integral with the first and second peripheralsidewalls.
 9. An electronic device comprising: a conductive housing,wherein the conductive housing comprises a rear wall and a peripheralsidewall, the rear wall has a first rear wall portion and a second rearwall portion that is electrically coupled to the first rear wallportion, the second rear wall portion is separated from the peripheralsidewall by a dielectric-filled slot, and the dielectric-filled slotsurrounds three sides of the second rear wall portion; and a fingerprintsensor that overlaps that second rear wall portion.
 10. The electronicdevice defined in claim 9, further comprising: an antenna, wherein therear wall forms an antenna ground for the antenna and the antenna groundhas an extended ground portion formed from the second rear wall portion.11. The electronic device defined in claim 9, wherein the electronicdevice has a first side, a second side, and a third side that isparallel to the second side, the peripheral sidewall extends across thefirst side of the electronic device, and the conductive housing furthercomprises: a first additional peripheral sidewall that runs along thesecond side; a second additional peripheral sidewall that runs along thethird side; a first dielectric-filled gap that separates the firstadditional peripheral sidewall from the peripheral sidewall; and asecond dielectric-filled gap that separates the second additionalperipheral sidewall from the peripheral sidewall.
 12. The electronicdevice defined in claim 11, wherein the dielectric-filled slot iscontinuous with the first and second dielectric-filled gaps.
 13. Theelectronic device defined in claim 11, wherein the first rear wallportion directly contacts the first additional peripheral sidewall andthe second additional peripheral sidewall.
 14. The electronic devicedefined in claim 9, wherein the first rear wall portion and the secondrear wall portion are formed from a continuous piece of metal.
 15. Theelectronic device defined in claim 9, further comprising: a connectorreceptacle, wherein the fingerprint sensor overlaps the connectorreceptacle.
 16. The electronic device defined in claim 9, furthercomprising: a flexible printed circuit on which the finger print sensoris mounted; and a display having a display module that overlaps thefirst rear wall portion, wherein at least some of the flexible printedis interposed between the display module and the first rear wallportion.
 17. An electronic device having a first face and an opposingsecond face, the electronic device comprising: a metal housing, whereinthe metal housing comprises peripheral conductive sidewalls that extendfrom the first face to the second face of the electronic device and arear wall having a first rear wall portion and a second rear wallportion, the second rear wall portion being separated from the firstrear wall portion by a dielectric-filled gap; a dielectric cover layerthat extends across at least some of the first face of the electronicdevice and between the peripheral conductive sidewalls, wherein anopening is formed in the dielectric cover layer; and a fingerprintsensor formed at the first face of the electronic device and within theopening in the dielectric cover layer.
 18. The electronic device definedin claim 17, further comprising: control circuitry; and a flexibleprinted circuit, wherein the fingerprint sensor is mounted to theflexible printed circuit and the flexible printed circuit comprisesmetal traces that convey fingerprint data from the fingerprint sensor tothe control circuitry.
 19. The electronic device defined in claim 18,wherein the fingerprint sensor comprises a dielectric member, aplurality of sensor electrodes formed on the dielectric member, and ametal ring that surrounds the dielectric member, and the metal ring isinterposed between the dielectric member and the dielectric cover layerat the first face of the electronic device.
 20. The electronic devicedefined in claim 19, further comprising: at least one additionaldielectric-filled gap that divides a given one of the peripheralconductive sidewalls, wherein the at least one additionaldielectric-filled gap extends from the first face to the second face ofthe electronic device.